GLOBEC Phase IV. Broad-scale Synthesis of the Bank-wide patterns of Pseudocalanus distribution and abundance Ann Bucklin 1, Meredith A. Bailey 1, and Dennis J. McGillicuddy 2 1 University of New Hampshire, Durham NH USA 2 Woods Hole Oceanographic Institution, Woods Hole MA USA

Phase IV. Broad-scale Pseudocalanus patterns OBJECTIVES 1) Complete data analysis and integrate patterns with other target species and any other taxa that are abundant and/or ecologically important; 2) Apply numerical, coupled biological / physical models to the Pseudocalanus spp. distributional data to infer processes from the patterns; and 3) Analyze, integrate, and synthesize patterns and processes of Pseudocalanus spp. with all zooplankton species; evaluate role(s) of each species in the Georges Bank ecosystem.

Phase IV. Broad-scale Pseudocalanus patterns HYPOTHESES 1)Maintenance of P. moultoni populations over the Bank results primarily from retention of individuals within the cyclonic gyre throughout the year. The spring population increase results primarily from reproduction of individuals retained over the Bank, and secondarily from transport of individuals from adjacent regions in the Gulf of Maine. 2)Source regions for P. newmani are on the Scotian Shelf; transport from these upstream regions causes the spring population increase on Georges Bank. The species becomes very abundant on the crest when the cyclonic gyre closes and retains copepods advected along the southern flank.

Phase IV. Broad-scale Pseudocalanus patterns APPROACH 1) Convert data as necessary to conform to the format for all broad-scale data sets; 2) Work with other investigators to identify approaches for data intercomparison; 3) Infer testable hypotheses from the observed patterns of distribution and abundance; 4) Test hypotheses using adjoint modeling to examine the relative role of population dynamic and physical transport processes; and 5) Explore the role of each species in the context of the Georges Bank ecosystem, including population dynamic process of all target and important non-target species.

Discrimination of Pseudocalanus spp. by SS-PCR  Despite their morphological similarity, Pseudocalanus moultoni and P. newmani are clearly divergent in mtCOI sequence, with 18% difference.  A simple molecular protocol, species-specific PCR (SS-PCR) is used to identify individual copepods of any life stage (Bucklin et al., 2001). Reactions are done in 96-well plates, with positive and negative controls.  For the U.S. GLOBEC samples, only adult females have been identified and mapped. From Bucklin et al. (1999, 2001)

1997 Broad-scale Pseudocalanus mapping  Vertically-integrated (0 – 40 m) objectively-analyzed monthly distributions of P. moultoni (top) and P. newmani (bottom) females based on U.S. GLOBEC Georges Bank 1997 Broad-scale Surveys. Pseudocalanus newmani Pseudocalanus moultoni From McGillicuddy & Bucklin (2002)

1997 Broad-scale Pseudocalanus modeling  Physical and biological controls on species’ distributions in Spring were examined by assimilating the 1997 Broad-scale observations into a coupled physical-biological model.  The forward problem was posed as an advection - diffusion - reaction equation for the copepod concentration.  The adjoint method of data assimilation was used to invert for the biological sources and sinks implied by the observed changes in abundance between surveys and the flow during the intervening period. From McGillicuddy and Bucklin (2002).

1997 Broad-scale Pseudocalanus Cartoons  In April, species’ distributions were distinct: P. moultoni was concentrated on the NW flank of Georges Bank; P. newmani predominated on southern flank of Georges Bank and southern tip of Browns Bank.  By June, advective transport and net growth of both species resulted in overlapping distributions. Circulation mixed two species from their respective source regions into an overall distribution that was centered over crest of Georges Bank. From McGillicuddy & Bucklin (2002) Sources RED; Sinks BLUE; Popuation centers GREEN; Advective impacts BLACK ARROWS

1999 Broad-scale Pseudocalanus mapping  Objectively-analyzed vertically-integrated (0 – 40 m) monthly distributions of P. moultoni (top) and P. newmani (bottom) females based on U.S. GLOBEC Georges Bank 1999 Broad-scale Surveys.  Spring-time evolution in 1999 similar to 1997: both species increase in abundance through March. Spread of P. moultoni may occur from western boundary; P. newmani may be transported from ‘upstream’ waters, around southern flank and onto crest.

1997 vs Broad-scale Pseudocalanus mapping  Spring-time evolution was similar in 1997 (top panels) and 1999 (bottom): abundance of both species increases through March, with P. moultoni transported from the western boundary onto the crest; P. newmani is carried from upstream, around southern flank, and onto crest

1999 Southern flank cross-frontal studies  Cross-frontal study on southern flank with Karen Wishner et al., June 1999  Pseudocalanus spp. collected in 10 m strata at three stations across the tidal mixing front, during different tidal phases and current flow directions.  Vertical distributions and abundances of the two species differed in ways that will affect likelihood of retention on the crest of Georges Bank.

 Currents measured by ADCP were used to estimate transport of copepods in the tidal mixing front area  P. moultoni were overall less abundant. Samples with highest concentrations of this species were more likely to experience on-Bank transport.  P. newmani were absolutely and relatively more abundant in surface waters and had significant concentrations in water flowing off- Bank.  Differences in vertical distributions of copepod species can have significant consequences for their patterns and pathways of advective transport and retention in stratified flow Southern flank cross-frontal studies

Phase IV. Planned activities Mapping Add species abundances for deep samples (below 40 m) with Pseudocalanus spp. >500 /m 2 for 1999 Broad-scale surveys, to increase completeness of the vertically integrated maps. [Completed August, 2003] Map adult female abundances for 1998 Broad-scale surveys for two strata (0 – 15 m and 15 – 40 m) Analysis Comparisons of seasonal cycles and depth distributions for Pseudocalanus spp. over the Bank Modeling Adjoint modeling of vertically-integrated 1999 monthly distributions January to June Publication Mapping and modeling of 1999 Broad-scale, with results from June 1999 cross-frontal experiment (with Karen Wishner et al.); comparison of 1997 and 1999 patterns and processes

Phase IV. Planned activies Expanded efforts with GLOBEC IV funding SS-PCR analysis of copepodite stages from 1999 Broad- scale MOCNESS samples, to allow stage-structured modeling Related efforts with other funding Analysis of adult females in NMFS NEFSC Ecosystem Monitoring Survey samples 2001 – 2003 (ZooGene) Analysis of adult females in REACH coastal monitoring transect samples beginning 2002 (UNH / COOA)

Pseudocalanus spp. beyond the Bank  In MARMAP surveys 1977 – 1987, Pseudocalanus spp. shows a seasonal cycle of abundance, with two population centers: Western Gulf of Maine Georges Bank  Davis (1984) hypothesized the Western Gulf of Maine is a source region for the Georges Bank population  McGillicuddy et al. (1998) concluded that the populations are functionally distinct, with geographically-specific regions of growth and mortality Color bars show concentration (# m -3 ) From McGillicuddy et al. (1998)

REACH: Regional Ecology and Coastal Hydrography  Vertically-stratified MOCNESS samples are collected from four stations along a cross-shelf transect from 60 – 110 m depth as part of the REACH (Regional Ecology and Coastal Hydrography) coastal monitoring project since April  Data collected include zooplankton species counts, CTD, fluorescence, chlorophyll, nutrients, and phytoplankton (including HAB-forming Alexandrium sp.) counts

Pseudocalanus spp. in the Western Gulf of Maine  The REACH transect samples were used to evaluate seasonal patterns by pooling species from all samples, including all four stations and throughout the water column.  Pseudocalanus spp. are present year-round in low abundances; Temora longicornis dominates during Summer; Oithona similis and Centropages typicus predominate in Fall. Density (#/m^3) Month

Pseudocalanus newmani Pseudocalanus moultoni Density/m 3  Pseudocalanus spp. occur throughout the year in REACH samples from the Western Gulf of Maine.  Under stratification, P. moultoni is more concentrated at depth; P. newmani is relatively more abundant at surface.  The two species show more similar patterns of vertical distribution in a fully-mixed water column. Relative Density Complete Mixing Start of Mixing Pseudocalanus newmani Pseudocalanus moultoni Pseudocalanus spp. in the Western Gulf of Maine

 Pseudocalanus spp. will be analyzed from stratified Broad-scale samples from 1999 in order to characterize vertical distributions.  Of particular interest are vertical distributions during stratification, when vertical positioning may largely determine retention and / or loss.  These data suggest that P. moultoni is more frequently in the lower half of the water column, while P. newmani can be most abundant in surface waters. Pseudocalanus spp. vertical distributions on the Bank May 1999

Pseudocalanus spp. in NEFSC Surveys  NMFS NEFSC Ecosystem Monitoring Surveys are conducted four times per year.  Surveys sample the NW Atlantic shelf region from the Mid-Atlantic Bight to the Gulf of Maine.  ~20 randomly-selected bongo-net samples are collected for ZooGene each cruise.  Temporal and spatial resolution is limited, but sufficient to allow us to speculate about the significance of ‘loss’ from Georges Bank for the survival of the species.  Analysis is underway, starting with samples from coastal stations in the Gulf of Maine collected during 2001 – 2003 surveys.